US stock markets rose after Federal Reserve chairman Ben Bernanke signalled a
willingness to introduce fresh stimulus even if he failed to provide the
specifics some investors wanted.

In an eagerly-anticipated speech at the annual gathering of central bankers in Jackson Hole, Wyoming, Mr Bernanke delivered a relatively downbeat picture of the world's largest economy five years on from the start of the financial crisis.

The high level of unemployment - it climbed to 8.3pc in July - is a "grave concern" the Fed chief said while admitting that the "economic situation remains far from satisfactory."

Although Mr Bernanke offered no clues as to what the Fed may do and when, his assessment of the economy seemed enough to convince investors that the central bank is likely to do more.

After dropping briefly after the release of the speech this afternoon, the Dow Jones Industrial Average was up 1.1pc at 13,139.70 in late morning trading on Wall Street and the S&P 500 climbed 0.6pc to 1,408.

"The Chairman is clearly hoping for another round of QE," said Chris Low, an economist at FTN Financial.

The minutes of last month's meeting of the rate-setters at the Fed had already shown that many are willing to embark on more stimulus unless the economy quickly shows a "substantial and sustainable".

As Americans head for a long Labor Day weekend, attention next week will focus on the monthly employment report for August that will be released on Friday. The Federal Open Market Committee - the equivalent of the Bank of England's Monetary Policy Committee - next meets the following week.

The Jackson Hole address came as there was slightly better news from America's manufacturing sector. New orders placed at US factories climbed 2.8pc in July, according to a report from the Commerce Department, reversing a 0.5pc drop in June.

Beyond a gloomy assessment of the economy, Mr Bernanke used the majority of the eagerly-anticipated address to defend the more than $2trillion of quantitative easing (QE) that the Fed has done since the US plunged into recession in 2009.

Those programmes, which saw the Fed buy US government bonds as well as mortgage-backed debt, helped save jobs and drive down interest rates, said Mr Bernanke.